Quote Originally Posted by cture
Or another one.
Match the spectrum to
420-490 30%
490-620 10%
620-700 60%
What kind of soft do you use to build spectra graphs, may I have a link?
Check the 4R3+CW+RB on post #8. It has almost the same distribution, except on the red range where it only reach up to 670nm. In order to get a less concentrated output on the red range and increase its bandwith up to 700nm (it should cover slighty after it) you can use 2R3 and 2 650-660nm peaked red leds, as the LedEngin ones. They are less efficients than the M bin of red Crees, but no so much you cant use them if you want to cover the longer part of the red range.

You should be aware than when choosing LEDs, you need to consider carefully not only models/brands, but bins of each one. Usally LEDs are binned according three parameters: luminoux flux, color and Vf (forward voltage).

For same model, often there are 3-4 color bins that cover the range. For example, red Crees are avalaible on R2 (620-625nm dominant wavelenght), R3 (625-630nm) and R4 (630-635nm) color bins, although they give up serving the R4 on the high power models (its only avalaible for the medium power XL4550 currently). There are aswell 3 color bin for the Royal Blues and more than 20 for coolwhite.

Luminosity bins determines LEDs efficiency. For same color bin, there are different light fluxes avalaible. As for same SPD, higher photometric flux (lm) means higher energy efficiency, and often top bin is more than double than bottom bin, almost any LED model have a very wide range of efficiencies.

We always should try to get top bins, but they are more expensive and not always avalaible.

Cree is currently the better manufacturer for InGan leds (Royal blue, Blue and white). They are a step forward the competence. They are serving currently up the bin group 15 for Royal Blues (>450mW@350mA) and up to bin Q5 on coolwhites (107-114lm@350mA) for the XR-E model.

There are some other manufacturers that are using the Cree EZBright1000 chip on their models, as Seoul Semiconductor, Edixeon and Kingbright. They are a cheaper alternative, but construction quality is often far from Cree ones. Osram has been licenced the EZBright too but its still unavalaible.

For the red side, Cree does good LEDs, but difference is smaller than for InGans. Indeed, Osram does more efficient red leds, but unfortunatelly Osram not allow to select a single bin as Cree or Lumileds.

So when selecting what LED model to use, its impossible to generalize: best choice would depend on what you can get on your situation, involving how many LEDs are you going to buy, where you live, if your distributor allows to select concrete bins, etc.

Although prices for manufacturers is very competitive and there is little differences, when an individual look for a given model/bin, differences may be very large.

So one thing is the ideal LEDs to use, and other what you can actually obtain, and price.

So it would be better to have a general idea of what models are valid for us, seek for them and select the best avalaible for you.

In the USA and Canada, for example, ordering from Future Electronics (official distributor of Lumileds) allows you to select individual bins and get decent prices still buying low quantities. They arnt the best LEDs avalaible, but probably they have the best price/perfomance for a northamerican.

And the other good source is Digikey, that distributes Osram at very competitive prices in NorthAmerica. Not bin selection allowed, but excelent average price/perfomance. For example, the red Argus (Golden Dragon with lenses, from 20º to 160º beam angles) is 1.64$ buying 200.

So i suggest you first look for what leds (models/bins) you have avalaible, and then select the best choice between them. I can help you on the selection, but i dont think it would be worthwhile to list the best model/bins possible if you cant access them.

I built those spectrums using OppenOffice (its a free suite equivalent (but better, IMHO) than MS Office. But ive uploaded the Bulb Analizer tool on Excel format too. Ive liked it on the Perfect LED grow light thread. I uploaded too the sheet for the Cree some post later, aswell as how to calculate the true radiometric output.

In order to build the spectra, ive used the Output percentual wavelenght column of the sheet. By multiplying it by the true radiometric output of the LED you get the normalized SPD so you can sum different LEDs SPDs and build spectra of any combination.